An almond allergy, like all food allergies, is caused by an immune reaction against a protein found in the food. Although almonds seem to cause the least allergy problems of all tree nuts, you can develop an allergy against the proteins found in the nut. Raw almond allergy can develop if you eat the nut and your immune system mistakes its proteins as harmful; the next time you eat almonds, your body quickly recognizes the protein and triggers an allergic reaction against it.
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Your immune system has evolved to protect you from foreign particles, such as bacteria, viruses and toxins. When your body encounters these harmful particles, your immune system works to destroy these invaders by engulfing them with white blood cells and eliminating them with antibodies. As a response to an immune reaction, your body generates molecules that promote inflammation to help clear the invading particles more optimally. Although most typically immune reaction is generated in response to harmful molecules, sometimes your immune system can mistaken a harmless foreign molecules such as proteins in food as dangerous.
Antibodies are effective mediators of immunity that recognize a specific molecule among millions of other molecules. Your body can generate specific antibodies against any foreign molecule. Once generated, antibodies bind to the molecule, such as a bacterial toxin or a protein found in the surface of a microbe, and helps eliminate the particle with the help of white blood cells or other immune molecules. There are five classes of antibodies, or immunoglobulins, that differ in their actions. The most common type is the IgG that is generated in response to microbial infections. Another antibody class, called the IgE, is generated in allergies and as a response to parasitic infections.
IgE antibody differs from other antibody classes by its ability to activate certain white blood cells including mast cells, basophils and eosinophils. IgE itself does not cause an allergy, but the activation of mast cells and the resulting production of immune mediators trigger an allergic reaction. If your body mistakes the almond protein as dangerous, it generates a specific IgE antibody against it. The IgE binds the protein and activates mast cells. Mast cells begin to secrete molecules that produce inflammation and allergy symptoms.
One of the mediators mast cells release is histamine, a vasoactive molecule that increases local blood flow, vascular permeability and smooth muscle contraction. When you eat almonds, within seconds your throat can swell and become inflamed due to these histamine actions in the tissue surrounding your mouth and throat. In severe cases, the mast cell activation can lead to systematic anaphylaxis that causes widespread vascular permeability, leading to a drop of blood pressure, airway constriction and difficulty breathing. This condition needs to be treated quickly with an epinephrine injection and can be fatal.